New Greenland Ice Sheet Data Will Impact Climate Change Models

With digital imaging techniques, scientists find new data in old aerial photographs

This satellite image, colored for emphasis and taken in 2001,
shows the ice sheet margins where land (pink areas) has become
exposed and lakes were formed (bright blue). The large bluish-green
area is the glacier.

Research conducted by a UB geologist on the Greenland ice sheet
shows the trimline (broken brown line) that marks the maximum
extent of the ice sheet at the end of the 18th century and the
subsequent retreat of the glacier and land exposed since 1944.

BUFFALO, N.Y. -- A comprehensive new study authored by
University at Buffalo scientists and their colleagues for the first
time documents in detail the dynamics of parts of Greenland's ice
sheet, important data that have long been missing from the ice
sheet models on which projections about sea level rise and global
warming are based.

The research, published online this month in the Journal of
Glaciology, also demonstrates how remote sensing and digital
imaging techniques can produce rich datasets without field data in
some cases.

Traditionally, ice sheet models are very simplified, according
to Beata Csatho, Ph.D., assistant professor of geology in the UB
College of Arts and Sciences and lead author of the paper.

"Ice sheet models usually don't include all the complexity of
ice dynamics that can happen in nature," said Csatho. "This
research will give ice sheet modelers more precise, more detailed
data."

The implications of these richer datasets may be dramatic,
Csatho said, especially as they impact climate projections and
sea-level rise estimates, such as those made by the United Nations
Intergovernmental Panel on Climate Change (IPCC).

"If current climate models from the IPCC included data from ice
dynamics in Greenland, the sea level rise estimated during this
century could be twice as high as what they are currently
projecting," she said.

The paper focuses on Jakobshavn Isbrae, Greenland's fastest
moving glacier and its largest, measuring four miles wide.

During the past decade, Jakobshavn Isbrae has begun to
experience rapid thinning and doubling of the amount of ice it
discharges into Disko Bay.

"Although the thinning started as early as the end of the 18th
century, the changes we are seeing now are bigger than can be
accounted for by normal, annual perturbations in climate," Csatho
said.

In order to document the most comprehensive story possible of
the behavior of Jakobshavn Isbrae since the Little Ice Age in the
late 1800s, Csatho and her colleagues at Ohio State University, the
University of Kansas and NASA used a combination of techniques.

These included field mapping, remote sensing, satellite imaging
and the application of digital techniques in order to glean
"hidden" data from historic aerial photographs as many as 60 years
after they were taken.

By themselves, Csatho explained, the two-dimensional pictures
were of limited value.

"But now we can digitize them, removing the boundaries between
them and turning several pictures into a single 'mosaic' that will
produce one data set that can be viewed in three-dimensions," she
said.

"By reprocessing old data contained in these old photographs and
records, we have been able to construct a long-term record of the
behavior of the glacier," said Csatho. "This was the first time
that the data from the '40s could be reused in a coherent way."

The data from the historic photos were combined with data from
historical records, ground surveys, field mapping and measurements
taken from the air to document important signs of change in the
glacier's geometry.

Csatho explained that conventional methods of assessing change
in glaciers have depended on documenting "iceberg calving," in
which large pieces at the front of the glacier break off.

"But we found that you can get significant changes in the ice
sheet without seeing a change in front," she said.

Other key findings of the paper are that two different parts of
the same glacier may behave quite differently and that a glacier
does not necessarily react to climate change as a single,
monolithic entity.

"Climate forces are complex," Csatho said. "For example, we
found that the northern part of Jakobshavn was still thinning while
the climate was colder between the 1960s and the 1990s."

Csatho, who is a geophysicist, added that the research is the
result of a strong interdisciplinary team involving experts in
glaciology, ice sheet modeling and photogrammetry, the science of
making measurements based on photographs.

At UB, research in Csatho's remote sensing laboratory -- http://rsl.geology.buffalo.edu/
-- focuses on a multidisciplinary approach that integrates
information across the geosciences.

Csatho's co-authors on the paper are Tony Schenk of the Ohio
State University Department of Civil and Environmental Engineering
and Geodetic Science; Kees van der Veen of the Center for Remote
Sensing of Ice Sheets at the University of Kansas, and William B.
Krabill of the National Aeronautics and Space Administration's
Cryospheric Sciences Branch.

The research was funded by the National Science Foundation and
NASA.

The University at Buffalo is a premier research-intensive
public university, a flagship institution in the State University
of New York system that is its largest and most comprehensive
campus. UB's more than 28,000 students pursue their academic
interests through more than 300 undergraduate, graduate and
professional degree programs. Founded in 1846, the University at
Buffalo is a member of the Association of American
Universities.